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Cell biology > Embryology > Flashcards

Embryology Flashcards

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1
Q

When is the embryonic period and the fetal period?

A

The embryonic period is the human development in utero in the first 8 weeks. The fetal period is the the remaining 32 weeks.

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2
Q

What are teratogens?

A

Factors that cause birth defects.

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3
Q

When are embryos most susceptible to teratogens?

A

Between the 3rd and 8th weeks of gestation

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4
Q

What are the four processes in embryology?

A

Growth, Differentiation, Cell migration and cell death

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5
Q

Describe ovulation

A

An ovum is released from the ovarian follicles and swept up into the oviduct by cilia and muscle contractions of the oviduct.

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6
Q

Where does fertilisation normally occur?

A

Normally occurs in the wide ampulla of the oviduct - the sperm having travelled from upper vagina through the uterus and into oviduct.

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7
Q

What does the sperm have to penetrate before it’s membrane can fuse with ovum?

A

Sperm must penetrate the cumulus oophorus, corona radiata and the zona pellucida around the ovum.

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8
Q

Describe the formation of the morula (until day 4)

A

Rapid cell division begins immediately following fertilisation, 1st division within 24hrs, 2nd within 48hrs, 6-12 cells by day 3 .
On day 4 the Morula undergoes compaction - tight junctions form between cells
2 sets of cells become distinct: inner cell mass and outer cell mass.

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9
Q

On day 4 what’s the inner cell mass called and what will it become?

A

Inner cell mass is called embryoblast, and it will form the embryo.

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10
Q

On day 4 what’s the outer cell mass called and what will it form?

A

The outer cell mass is called the trophoblast and it will form part of the placenta.

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11
Q

Describe the formation of the blastocyst and where the inner cell mass lies…

A

On day 4/5 the morula becomes leaky and fluid enters the ball of cells and the morula is now transformed into a hollow blastocyst.
The inner cell mass lies at the embryonic pole of the blastocyst.

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12
Q

Describe day 6…

A

The blastocyst hatches from the zona pellucida and begins to implant in the endometrium, this is known as the secretory phase as it begins to grow under the influence of progesterone released from the corpus luteum.

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13
Q

What cells secrete hCG and what does it do?

A

trophoblast cells release hCG ( human chorionic gonadotrophin) and this maintains the uterine lining.

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14
Q

When are hCG levels high enough to be detected by pregnancy test?

A

By the end of the second week.

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15
Q

Why is the embryo not attacked by immune system?

A

The implanted embryo employs mechanisms to suppress the immune system and block recognition as a foreign tissue so mothers immune system does not attack it.

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16
Q

What percentage of blastocysts fail to implant?

A

10%

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17
Q

What percentage of detected pregnancies miscarry and what is the realistic number?

A

15% but more like 50%

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18
Q

What is an ectopic pregnancy?

A

Where the blastocyst implants in an abnormal site such as the peritoneal cavity or oviduct- normally die in their 2nd month

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19
Q

What layers does the trophoblast differentiate into in week 2?

A

Cytotrophoblast and Syncitiotrophoblast

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20
Q

What layers does the embryoblast differentiate into in week 2?

A

Epiblast and hypoblast

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21
Q

What are the epi and hypoblast known as?

A

Bilaminar germ disc

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22
Q

What cells line the original blastocyst cavity in week 2?

A

Hypoblast cells

23
Q

What does the original blastocyst cavity form and what is it filled with?

A

Forms the yolk sac which is filled with fluid - NO YOLK

24
Q

What is the name of the new layer that yolk sac cells form in week 2?

A

The extraembryonic mesoderm

25
Q

What is the extraembryonic mesoderm?

A

It forms the connecting stalk, it is the precursor to the umbilical cord.

26
Q

What are lacuna?

A

Gaps in the syncitiotrophoblast

27
Q

What happens to lacunae?

A

blood from maternal capillaries begins to fill the lacunae, beginning of the uteroplacental circulation.

28
Q

What are sinusoids?

A

Large capillaries in endometrium for uteroplacental circulation formed from lacunae.

29
Q

What are the three cavities in week 2?

A

Amniotic cavity
Yolk sac
Extraembryonic cavity (chorionic cavity)

30
Q

What are the epiblast and hypoblast sandwiched together between in week 2?

A

Sandwiched between yolk sac and amniotic cavity, forming bilaminar germ disc.

31
Q

When does the primitive streak appear?

A

Week 3

32
Q

What does the primitive streak establish?

A

Longitudinal axis and bilateral symmetry

33
Q

What is gastrulation?

A

Process that establishes 3 germ layers in the 3rd week

34
Q

What do cells of the epiblast do in week 3?

A

Proliferate and migrate towards the primitive streak, the cells become flask shamed and detach from epiblast and slip beneath it - known as invagination.

35
Q

What forms after cells invaginate?

A

Some cells displace hypoblast forming the embryonic endoderm.
Some lie between epiblast and endoderm to form mesoderm.
Cells remaining in epiblast now form ectoderm.
These three form the trilaminar disc.

36
Q

What’s the trilaminar disc made of?

A

Endoderm, ectoderm and mesoderm

37
Q

What happens to Buccopharangeal membrane in week 4?

A

Perforate to form mouth opening

38
Q

What happens to cloacal membrane in week 7?

A

Will perforate to become opening of anus and urogenital tracts

39
Q

What does high doses of alcohol do and what does it affect?

A

Kill cells in anterior midline of germ disc- affects face and brain development

40
Q

What’s sinus invertus?

A

Transposed thoracic and abdominal viscera- Organ defects

41
Q

What is sarococcygeal teratomas?

A

Most common tumour in newborns- formed from persist at remains if primitive streak

42
Q

What does the Ectoderm go on to form?

A

Forms epidermis and nervous tissue

43
Q

What does the mesoderm go on to form?

A

Skeletal, muscular and circulatory systems/ connective tissues

44
Q

What does Endoderm go on to form?

A

Forms digestive and respiratory tracts.

45
Q

What’s the notochord later replaced by?

A

Vertebral column

46
Q

What does the notochord secrete and what do they do?

A

Substances such as noggin and chordin which inhibit the growth factor BMP4 causing overlying ectoderm cells to form neural plate.

47
Q

What’s happens to flat neural plate in week 4?

A

Rolls up to form the neural chord

48
Q

What does the neural tube go on to form?

A

Brain and spinal chord

49
Q

What does the other ectoderm become?

A

Epidermis

50
Q

What forms the ear and lens of eye?

A

Otic and lens placodes which are thickening’s of the ectoderm.

51
Q

What are the other 3 things ectoderm forms?

A

Subcutaneous glands, pituitary glands and tooth enamel

52
Q

What does paraxial mesoderm form in week 4?p and what are they called.

A

Paraxial mesoderm forms paired segments: somites, they appear in a craniocaudal sequence

53
Q

What does each somite divide into ?

A

Sclerotome, myotome, dermatome,

54
Q

The notochord and neural tube induce sclerotome to do what?

A

Differentiate

Cell biology (2 decks)

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